Priority is claimed with respect to Japanese Application No. 046103/2000 filed on Feb. 23, 2000 in the Japanese Patent Office, the disclosure of the application is herein incorporated by reference.
1. Field of the Invention
The present invention relates to an ultrasonic sealing apparatus for use in a filling/packing machine for producing liquid beverages or the like packed in paper containers. More specifically, the present invention relates to the ultrasonic sealing apparatus provided with a stopper to regulate the distance between a sealing face of a horn and an action face of an opposing jaw for improved sealability by controlling the distance between the sealing face of the horn working as a sealing jaw and the action face of an opposing jaw.
2. Description of the Related Art
Hitherto, there has been known a filling/packing machine as a whole shown in FIG. 1. This packing machine contained a packing material web for a rectangular parallelepiped packing container filled with a sterilized juice.
The filling/packing machine has a rewinder 2 supporting a laminated packing material web 1 in a rolled state. It has a sterilization device 3 for sterilizing a tabular laminated packing material web successively rewound from the rewinder. It also has a longitudinal sealing section 4 for sealing longitudinal both end portions of the sterilized laminated packing material web and thereby forming a tubular laminated packing material web. It contains a liquid supply tube 5 for filling a fluid content into the web formed into a tubular form, a transverse sealing device 7 for transversely sealing the tubular laminated packing material web in the direction perpendicular to the longitudinal direction thereof in liquid, while feeding downward a tube filled with content by the length substantially corresponding to one package. Also, and at the same time, it continuously forms pillow-shaped containers 6 that are rectangular in section, and a container shaping device for forming the pillow-shaped containers 6 into rectangular parallelepiped containers 8, their final form, by folding their end portions. A sealing tape 9 is often used in forming a laminated packing material web into a tubular form. The transverse sealing device 7 is composed of a sealing jaw with a heat source, an opposing jaw for heat sealing in cooperation with the sealing jaw, and driving means to drive these sealing jaws and the opposing jaw.
Further, as an ultrasonic sealing apparatus, there is the ultrasonic sealing apparatus which comprises a piezoelectric driving unit with a piezoelectric ceramic plate or a magnetostriction driving unit, which is connected to an AC supply source, and a horn with an elongated sealing surface, and which is further characterized with one or more reaction bodies forming a half wavelength together with the horn (Japanese Laid-Open Patent Application No. 2231/1995). In addition other ultrasonic sealing apparatuses are known (Japanese Patent Publication No. 22784/1987, Japanese Patent Publication No. 2544450/1996, Japanese Laid-Open Patent Application No. 33121/1995, Japanese Laid-Open Patent Application No. 92046/1981, Japanese Laid-Open Patent Application No. 15741/1994, and the like).
Pressing on an appropriate timing (applying pressure) is required for an ultrasonic sealing apparatus aiming at high-speed filling/packing operation. There arises a problem, however, that when a tubular packing material is pressed on an appropriate timing at transverse sealing, sealing pressure reaches at the required level when softening/melting condition of a thermoplastic resin of the packing material is still insufficient, therefore, an excellent sealing formation is prevented.
An object of the present invention is to provide an ultrasonic sealing apparatus capable of supplying sufficient output energy, delivered by an ultrasonic wave-generating device, to a thermoplastic resin of a packing material even when a tubular packing material is pressed on an appropriate timing at transverse sealing, so that softening/melting of the thermoplastic resin of the packing material is sufficient enough to provide an excellent sealing.
As a cause for insufficient softening/melting of a thermoplastic resin of a packing material as described above, a lower level of output energy delivered by an ultrasonic wave-generating device to a packing material than the required set point was first considered. Therefore, output power level delivered by an ultrasonic wave-generating device at pressing was measured in time course using a voltage recording device (Omnilight, Nippondenkisanei Co. Ltd.). As shown in FIG. 2, the output power level shows an extensive rightward increase in the diagram in the course of time. This rightward-up diagram suggests by its broken line in FIG. 2 that the output power level could go beyond the maximum output power allowance (output power 100%) of an ultrasonic wave-generating device when trying to supply sufficient energy for sealing
The following is considered to be a possible cause of this phenomenon. When the ultrasonic wave is delivered to a packing material under a pressed condition, the inmost thermoplastic resin layer of the packing material softens, consequently the sealing face of the horn and the action face of the opposing jaw rapidly comes closer to each other, especially when the pressing is done on an appropriate timing, and then rapidly changes into a vibrating system including the opposing jaw. When the output power level is higher than the maximum output power allowance of the ultrasonic wave-generating device (output power 100%), the protecting circuit starts to work and the ultrasonic wave delivery comes to a halt, meaning that only the energy corresponding to the dimension of the shadowed portion in FIG. 2 is delivered to the packing material.
The study lead to the conclusion that the structure as such that the sealing face of the horn and the action face of the opposing jaw do not come closer to each other more than a certain distance even when being pressed on an appropriate timing by regulating the distance between a sealing face of a horn having an elongated and flat sealing face and an action face of an opposing jaw including a pressing portion for pressing a packing material in cooperation with the sealing face of the horn, makes it possible to deliver energy corresponding to the dimension encircled by the line in FIG. 2 to the packing material. By this an excellent ultrasonic heat sealing can be achieved. Here, the invention is completed based on the above study.
The present invention, therefore, relates to an ultrasonic sealing apparatus in which a packing material consists of a laminated body containing at least a thermoplastic resin layer is formed into a tubular form. The tubular laminated packing material is transversely ultrasonically sealed, comprising a horn having an elongated and flat sealing face, an opposing jaw provided with an action face including a pressing portion for pressing a packing material in cooperation with the sealing face of the horn. The present invention also contains a stopper which regulates the distance between the sealing face of the horn and an action face of the opposing jaw. An ultrasonic sealing apparatus according to the invention is characterized in that it comprises a stopper regulating the distance between the sealing face of the horn and the action face of the opposing jaw to be smaller than that of when the tubular packing material is pressed under the non-molten condition by the horn and the opposing jaw. The stopper must be larger than that of when pressed under the molten condition. The invention also includes: an ultrasonic sealing apparatus, wherein the distance between the sealing face of the horn and the action face of the opposing jaw is smaller than that of when. the tubular packing material is pressed under the non-molten condition by 0.1-0.8 mm; an ultrasonic sealing apparatus, wherein the stopper is fixed to supporting members of the ultrasonic wave-generating device; an ultrasonic sealing apparatus, wherein the action face of the stopper is capable of butting against the action face of the opposing jaw through the tubular packing material which is pressed under the non-molten condition; an ultrasonic sealing apparatus, wherein the stopper is fixed to the opposing jaw; an ultrasonic sealing apparatus, wherein the action face of the stopper directly butts against the action face of stopper receiving members that are fixed to supporting members of the ultrasonic wave-generating device; an ultrasonic sealing apparatus, wherein a laminated body includes paper layer; an ultrasonic sealing apparatus, wherein the opposing jaw is provided with a cutting device; and an ultrasonic sealing apparatus, characterized in that when the tubular packing material is formed into a tubular form, the tubular packing material is formed into the tubular form by using a sealing tape.